Conventional color sense abnormality detectors, also know as anomaloscopes, such as those available from Nagel, Bausch & Lamb, and Double Dichroic Polaroid, comprise only three channels for red, green and yellow light sources in which light rays from the mixed red and green light sources are used to match the yellow light ray, and the red and green light rays are mixed in varied proportions such that ordinary subjects can be divided into two categories, i.e., subjects with normal color sense and those with abnormal color sense. Also, the color sense abnormality detector of the present invention can be used to screen from the subjects having the so-called "normal color sense" those whose red/green color senses are abnormal but who can be classified into groups with color weaknesses in red and green.
According to the principles of conventional color sense abnormality detectors, red and green lights of single wavelength (for different detectors, light sources of different wavelengths may be selected), after being mixed in adjustable proportions, are used to compare with yellow light of fixed wavelength. The brightness of the light from this yellow light source can, of course, be adjusted by the subjects themselves. The comparison is made optically in which the mixed red and green lights are caused to produce a partite and color match (i.e., of uniform color and same brightness) is made with the yellow light of the other partite. The full circle formed of two partitions is referred to as a bipartite field (see FIG. 1). If the colors of both partitions are uniform and the brightnesses the same, the bipartite field becomes a uniform circle showing yellow light. The subjects are allowed free to adjust the proportion of the red and green lights such that when color match is effected different ratios of red to green lights from those for normal persons will be obtained with respect to the subjects possibly due to the fact that they are color weak or blind in red and green.
These conventional detectors, however, can be applied only for detecting cases of color weakness or blindness in that for a subject with glaucoma whose blue cones could be damaged due to the overpressure in his eyes. Then, the subject with weakened function of the blue cones will be unable to perform the color light match which involves such blue cones. This compares to the fact that with a deflated rubber ball, it will not rebound high regardless the physical strength which is used to strike it. In other words, the ball is not sensitive enough to the externally applied force so as to rebound to the corresponding height. Similarly, when the function of the blue cones is weakened, it is impossible to produce a reaction in proportion relative to the stimulation in varied degrees and proportions of the blue light received externally. For such types of subjects, the reaction produced by the stimulation from light with blue component is "inert", then, apparently, it is necessary to carry out a test that is specifically directed to the blue cones.